1. Field
One or more example embodiments relate to cross point memory arrays, methods of manufacturing the same, masters for imprint processes, and methods of manufacturing masters. More particularly, one or more example embodiments relate to cross point memory arrays including a variable resistance material as a storage node, methods of manufacturing the same,' masters for imprint processes, which are used to manufacture cross point memory arrays, and methods of manufacturing masters.
2. Description of the Related Art
Conventional semiconductor memory arrays include a plurality of unit memory cells. An example of a volatile semiconductor memory is a dynamic random access memory (DRAM). In a conventional DRAM, each unit memory cell includes a switch and a capacitor. Conventional DRAMs are relatively highly integrated and have relatively fast operating speeds. But, DRAMs are volatile in that after power to the DRAM is turned off, all data stored in the DRAM is lost.
A conventional flash memory, on the other hand, is an example of a non-volatile memory device. In a conventional flash memory device all data stored in the non-volatile memory device is retained even after power to the non-volatile memory device is turned off. Conventional flash memories have non-volatile properties, but have lower integration degree and slower operating speeds as compared to conventional DRAMs.
At present, non-volatile memory devices, such as magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase-change random access memory (PRAM), and resistance random access memory (RRAM) are being studied. In one example, to store data a RRAM uses a variable resistance property of a transition metal oxide material, for example, a property in which the resistance of the transition metal oxide material varies according to the state of the RRAM.
RRAMs have been studied based on a cross point array structure in which a plurality of lower electrodes and a plurality of upper electrodes cross one another. A storage node is formed at each point in which the plurality of lower electrodes and the plurality of upper electrodes cross one another. Random access is possible in the cross point array structure, and thus, data reading and writing may be performed more easily. However, when reading and writing data, a current path is formed between the cross point array structure and a storage node that is adjacent to the cross point array structure, thereby resulting in a leakage current. To reduce the leakage current in the cross point array structure, a switching structure is formed together with the storage node.
Various technologies for transferring semiconductor patterns to manufacture a semiconductor device, such as a resistive memory device, have been developed. The technology that is mostly used for transferring semiconductor patterns is photolithography such as electron beam (E-beam) lithography technology and X-ray exposure technology using radiation light. These types of photolithography are used to manufacture a mask for photolithography and to form fine patterns. In these technologies, as semiconductor patterns become more precise, the cost for manufacturing a semiconductor device increases. In addition, in E-beam lithography photolithography, patterns have a two-dimensional (2D) structure in which the shape of patterns formed in an exposed region and the shape of patterns formed in an unexposed region are relatively simple. Thus, there is a limitation in forming various patterns.
Nano-imprint lithography (NIL) has been found to be a relatively effective and relatively economical alternative technology for forming patterns. NIL is a technology suggested for performing a nano-process (e.g., about 1 nm to about 100 nm, inclusive) as an ultra-fine process. In NIL, mold patterns are directly transferred onto a substrate by using a press method. A thermoplastic resin or a photocurable resin is coated on the substrate, pressurized with a nano-sized mold by using heat or ultraviolet (UV) rays, and cured to transfer the mold patterns. By using NIL, a stepped portion may be formed more conveniently on a substrate to be processed. A general photolithography process is finished with a one press transferring process, and thus, NIL is more effective for forming a multi-stepped shape. It has also been reported that NIL may be used in a process of manufacturing an electronic device such as a metal oxide semiconductor field effect transistor (MOSFET) or an optical device, instead of the general photolithography process.